Stop Outlook's "Reminder" from popping up
Solution 1:
In Outlook 2007, that would be:
- Tools
- Options...
- "Other" tab
- Advanced Options
- Reminder Options...
- Uncheck "Display the reminder"
Solution 2:
In Outlook 2015 this option is in a slightly different place, but is easily accessible via File → Options → Advanced Options → Reminders Heading.
Solution 3:
For Outlook365 simply go to: File -> Options -> Advanced. There are some options for "Reminders". Just check the box "Automatically dismiss reminders for past calendar events". Problem should be gone. Good luck.